The present invention relates to a curable composition, and more particularly to a curable composition suitable for use as a coating to various materials such as outer walls of buildings, automobiles, industrial equipments, steel furnitures, household electric appliances and plastics, especially as a coating for applications required to have excellent durability.
Top coatings applied to outer surface of buildings or building materials or automobiles, or maintenance coatings are required to have both an excellent durability and an excellent film appearance. As a means for improving the film appearance, a coating composition has been used as a high build coating. Conventional coating compositions are, however, poor in sag resistance (property capable of forming a thick film by one application without sagging), so a thickness of a coating film per one application is at most 30 .mu.m. Accordingly, the application of the coating composition must be repeated twice or more in order to obtain a film thickness of 50 .mu.m or more.
In order to improve the sag resistance of acrylic melamine coating compositions, Japanese Unexamined Patent Publication No. 2-4629, No. 58-129065 or No. 49-97026 has reported to add fine particles of a cross-linked polymer to the coating composition. According to these methods, though the sag resistance of the acrylic melamine coating composition can be improved, the obtained effect is insufficient, and as to alkoxysilyl group-containing acrylic copolymer coating compositions, the sag resistance is not improved.
Not only in order to economize in energy but also in order to nurse resources, it has been desired to form a thick film by one application of the coating composition. According to known techniques, the obtained film is unsatisfactorily thick, and a technique capable of forming thicker film is required.
An object of the present invention is to provide a curable composition having an improved sag resistance and capable of forming a thick film with an excellent appearance.
This and other objects of the present invention will become apparent from the description hereinafter.